So to calculate percentage after decreases you. Step 1) Get the percentage of the original number. If the percentage is an increase then add it to 100, if it is a decrease then subtract it from 100. Step 2) Divide the percentage by 100 to convert it to a decimal. Step 3) Divide the final number by the decimal to get back to the original number. Then you apply this formula to the equation to get the answer.
and inner radius 
![\displaystyle V = \int_0^1 \pi\Big[ \left( 2 - x^2 \right)^2 - \left( 2 - \sqrt{x}\right)^2\Big] dx](https://tex.z-dn.net/?f=%5Cdisplaystyle%20V%20%3D%20%5Cint_0%5E1%20%5Cpi%5CBig%5B%20%5Cleft%28%202%20-%20x%5E2%20%5Cright%29%5E2%20-%20%5Cleft%28%202%20-%20%5Csqrt%7Bx%7D%5Cright%29%5E2%5CBig%5D%20dx)
